Heat exchanger column

ABSTRACT

Plate-and-fin core-type heat exchangers are installed within pressure vessels in a manner which eliminates the need for distributors, collectors, headers, nozzles, and manifolds at the feed inlet, the processed gas outlet, or both the feed inlet and the processed gas outlet of each exchanger core. The heat exchangers can be installed in parallel or in series within a single pressure vessel. Alternatively, the heat exchangers can be installed in pressure vessels which are arranged in series such that multiple liquid product streams can be obtained. The heat exchangers preferably are operated in the condensing mode in which feed gas is cooled and partially condensed. The operation of the heat exchangers is characterized by the cocurrent flow of the condensate and uncondensed feed gas, preferably in the vertical or near-vertical direction. In an alternative embodiment, the heat exchangers are operated such that a feed fluid is cooled without phase change.

BACKGROUND OF THE INVENTION

[0001] Plate-and-fin or core-type heat exchangers are widely used in theprocess industries for the exchange of heat between fluid mixtures,particularly those which contain components with sub-ambient boilingpoints. These well-known heat exchangers are typically constructed withparallel plates separated by fins wherein the plates and fins are brazedtogether to form an integrated assembly of alternating flow channels.The most widely-used material for fabrication of these exchangers isaluminum.

[0002] The characteristic operating feature of core-type heat exchangersis the cooling of a first fluid stream, which flows through a firstgroup of flow channels or passageways, by indirect heat transfer with asecond fluid stream, which is warmed in another group of flow channels.The first and second fluid streams generally flow through alternatingchannels in order to maximize the effective heat transfer area of theexchanger. Additional fluid streams can be warmed and/or cooled inadjacent channels in the same heat exchanger, and thus core-typeexchangers can transfer heat among multiple fluid streams.

[0003] In a typical application, a gas is cooled and condensed byindirect heat transfer with a warming fluid such as a vaporizing liquidprocess stream or refrigerant. In the condensation mode of operation, afeed gas mixture is cooled and partially condensed within a group offlow channels by indirect heat transfer with one or more refrigerants orcolder fluids flowing in adjacent alternating flow channels.

[0004] An important requirement for the efficient operation ofplate-and-fin core-type heat exchangers is the proper distribution ofeach process stream into the heat exchanger so that the stream flowsuniformly through each of the desired flow channels. This isaccomplished by the use of feed distributor fins, headers, and nozzleswhich are joined to the inlet of the heat exchanger assembly. Inaddition, similar collector fins, headers, and nozzles are required towithdraw the process streams evenly from the outlet end of the heatexchanger. These distributor and collector devices are complex andexpensive. When multiple, parallel heat exchangers are required, complexand expensive manifolding also is required to distribute flow to andcollect flow from the parallel heat exchangers. Dome headers eliminatethe distributor fins or collector fins. However, these distributor andcollector devices typically cannot be used on cores larger than about 3feet by 4 feet in cross section at pressures above about 150 psig.

[0005] Because these heat exchangers often are used in the processing oflow-boiling gas mixtures, the resulting low-temperature operationtypically requires the use of cold boxes to contain the heat exchangers,phase separators, and associated piping.

[0006] Low-temperature gas processing plants, which utilize the complexheat exchange equipment described above, are highly capital-intensive.There is an ongoing need to reduce the capital cost and equipmentcomplexity of these plants, while retaining high operating efficiency.The invention described below and defined by the claims which followmeets this need by reducing or eliminating the use of complex feed gasdistributors and collectors, and optionally by eliminating the need forcold boxes to contain the heat exchangers and associated piping.

BRIEF SUMMARY OF THE INVENTION

[0007] A first embodiment of the invention is a system for cooling afluid feed stream which comprises:

[0008] (a) a pressure vessel having an interior and an exterior;

[0009] (b) a heat exchanger installed in the interior of the pressurevessel, wherein the heat exchanger comprises a group of flow passagewayswhich has a first end and a second end, wherein at least one of thefirst end and the second end is open and in flow communication with theinterior of the pressure vessel;

[0010] (c) inlet piping means for introducing the fluid feed stream intothe interior of the pressure vessel;

[0011] (d) outlet piping means for withdrawing from the interior of thepressure vessel at least a portion of the cooled fluid stream;

[0012] (e) cooling means for indirectly cooling the group of flowpassageways to cool the fluid feed stream therein to form a cooled fluidstream; and

[0013] (f) fluid transfer means for transferring the fluid feed streamfrom the inlet piping means into the group of flow passageways at oneend thereof or for transferring a cooled fluid stream from one end ofthe group of flow passageways to the outlet piping means.

[0014] In this first embodiment, the heat exchanger can be constructedin a plate-and-fin configuration.

[0015] The system described above can further comprise

[0016] (g) an additional pressure vessel having an interior and anexterior;

[0017] (h) a heat exchanger installed in the interior of the additionalpressure vessel, wherein the heat exchanger comprises a group of flowpassageways which has a first end and a second end, wherein at least oneof the first end and the second end is open and in flow communicationwith the interior of the additional pressure vessel;

[0018] (i) inlet piping means for introducing an intermediate fluidstream into the interior of the additional pressure vessel;

[0019] (j) cooling means for indirectly cooling the group of flowpassageways to cool the intermediate fluid stream therein to form anadditional cooled fluid stream;

[0020] (k) outlet piping means for withdrawing from the interior of theadditional pressure vessel at least a portion of the additional cooledfluid stream; and

[0021] (l) fluid transfer means for transferring the fluid feed streamfrom the inlet piping means into the group of flow passageways at oneend thereof or for transferring a cooled fluid stream from one end ofthe group of flow passageways to the outlet piping means.

[0022] The system described above can further comprise piping meansconnecting the outlet piping means of (d) with the inlet piping means of(i) such that at least a portion of the cooled fluid stream withdrawnfrom the pressure vessel can provide the intermediate fluid stream tothe additional pressure vessel.

[0023] The cooling means of (e) described above can comprise

[0024] (1) one or more additional groups of flow passageways in the heatexchanger wherein each additional group of flow passageways has a firstend and a second end, and wherein each additional group of flowpassageways is in indirect heat transfer communication with the group offlow passageways of (b);

[0025] (2) inlet piping means for introducing refrigerant into theinterior of the pressure vessel;

[0026] (3) outlet piping means for withdrawing warmed refrigerant fromthe interior of the pressure vessel;

[0027] (4) inlet distributor means for distributing the refrigerant fromthe inlet piping into the first end of the additional group of flowpassageways; and

[0028] (5) outlet collector means for collecting the warmed refrigerantfrom the second end of the additional group of flow passageways anddirecting warmed refrigerant into the outlet piping means.

[0029] In a first alternative of the system described in the firstembodiment above, the first end of the flow passageways can be an upperend and the second end of the flow passageways can be a lower end, andthe lower end can be open and in flow communication with a lower regionin the interior of the pressure vessel. In this first alternative, theheat exchanger can be constructed in a plate-and-fin configuration.

[0030] The fluid transfer means described in (l) above can compriseoutlet manifold means and outlet header means for transferring a cooledfluid stream from the upper end of the group of flow passageways to theoutlet piping. The inlet piping means can be connected to a lower end ofthe pressure vessel and the outlet piping means can be connected to anupper end of the pressure vessel such that fluid can flow through thegroup of flow passageways in a generally upward direction. In this case,the fluid transfer means comprises inlet manifold means and inlet headermeans for transferring the fluid feed stream from the inlet piping intothe upper end of the group of flow passageways.

[0031] Alternatively, the inlet piping means can be connected to anupper end of the pressure vessel and the outlet piping means can beconnected to a lower end of the pressure vessel such that fluid can flowthrough the group of flow passageways in a generally downward direction.In this case, the fluid flowing generally downward through the group offlow passageways can be a gas which can condense therein to form a vaporand a liquid which flow into the lower end of the pressure vessel,wherein the outlet piping means of (d) is used for withdrawing vaporfrom the lower end of the pressure vessel, and wherein the systemincludes additional outlet piping means used for withdrawing liquid fromthe lower end of the pressure vessel.

[0032] In this first alternative of the first embodiment, the system canfurther comprise

[0033] (g) an additional pressure vessel having an interior and anexterior;

[0034] (h) a heat exchanger installed in the interior of the additionalpressure vessel, wherein the heat exchanger comprises a group of flowpassageways which has a first end and a second end, wherein at least oneof the first end and the second end is open and in flow communicationwith the interior of the additional pressure vessel;

[0035] (i) inlet piping means for introducing an intermediate fluidstream into the interior of the additional pressure vessel;

[0036] (j) inlet fluid transfer means for transferring the intermediatefluid stream from the inlet piping means into the group of flowpassageways at one end thereof;

[0037] (k) cooling means for indirectly cooling the group of flowpassageways to cool the intermediate fluid stream therein to form anadditional cooled fluid stream; and

[0038] (l) outlet piping means for withdrawing from the interior of thepressure vessel at least a portion of the additional cooled fluidstream.

[0039] The system can further comprise piping means connecting theoutlet piping means of (d) with the inlet piping means of (i) such thatat least a portion of the vapor withdrawn from the pressure vessel canprovide the intermediate fluid stream to the additional pressure vessel.This heat exchanger in the additional pressure vessel can be constructedin a plate-and-fin configuration.

[0040] The inlet piping means can be connected to an upper end of theadditional pressure vessel and the outlet piping means can be connectedto a lower end of the additional pressure vessel such that vapor canflow through the group of flow passageways in a generally downwarddirection. In this case, the vapor flowing generally downward throughthe group of flow passageways can condense therein to form anuncondensed vapor and a liquid which flow into the lower end of theadditional pressure vessel, wherein the outlet piping means of (I) isused for withdrawing the uncondensed vapor from the lower end of theadditional pressure vessel, and wherein the system includes additionaloutlet piping means used for withdrawing liquid from the lower end ofthe additional pressure vessel.

[0041] In a second alternative of the first embodiment described above,the first end of the flow passageways can be an upper end and the secondend of the flow passageways can be a lower end, and wherein the upperend can be open and in flow communication with an upper region in theinterior of the pressure vessel. The heat exchanger in the pressurevessel can be constructed in a plate-and-fin configuration. The fluidtransfer means can comprise inlet manifold means and inlet header meansfor transferring the fluid feed stream from the inlet piping into thelower end of the group of flow passageways. In one mode of this secondalternative, the inlet piping means can be connected to a lower end ofthe pressure vessel and the outlet piping means can be connected to anupper end of the pressure vessel such that fluid can flow through thegroup of flow passageways in a generally upward direction. In this case,the fluid transfer means comprises outlet manifold means and outletheader means for transferring the cooled fluid stream from the lower endof the group of flow passageways to the outlet piping means. In anothermode of this second alternative, the inlet piping means can be connectedto an upper end of the pressure vessel and the outlet piping means canbe connected to a lower end of the pressure vessel such that fluid canflow through the group of flow passageways in a generally downwarddirection.

[0042] A second embodiment of the invention is a system for cooling afluid feed stream which comprises:

[0043] (a) a pressure vessel having an interior and an exterior;

[0044] (b) a heat exchanger installed in the interior of the pressurevessel, wherein the heat exchanger comprises a group of flow passagewayshaving a first end and a second end, wherein the first end is open andin flow communication with a first end of the interior of the pressurevessel and the second end is open and in flow communication with asecond end of the interior of the pressure vessel;

[0045] (c) cooling means for indirectly cooling the group of flowpassageways to cool the fluid feed stream therein to form a cooled fluidstream;

[0046] (d) inlet piping means for introducing the fluid feed stream intothe first end of the interior of the pressure vessel;

[0047] (e) outlet piping means for withdrawing at least a portion of thecooled fluid stream from the second end of the interior of the pressurevessel; and

[0048] (f) seal means disposed in the pressure vessel at an axiallocation between the first and second ends of the group of flowpassageways, which seal means isolates the first end of the interior ofthe pressure vessel from the second end of the interior of the pressurevessel such that the first and second ends of the interior of thepressure vessel are not in flow communication.

[0049] The heat exchanger in this second embodiment can be constructedin a plate-and-fin configuration.

[0050] In one alternative of this second embodiment, the inlet pipingmeans can be connected to a lower end of the pressure vessel and theoutlet piping means can be connected to an upper end of the pressurevessel such that fluid can flow through the group of flow passageways ina generally upward direction. In another alternative, the inlet pipingmeans can be connected to an upper end of the pressure vessel and theoutlet piping means can be connected to a lower end of the pressurevessel such that fluid can flow through the group of flow passageways ina generally downward direction. In this second alternative, the fluidflowing generally downward through the group of flow passageways can bea gas which can condense therein to form a vapor and a liquid which flowinto the lower end of the pressure vessel, wherein the outlet pipingmeans of (e) is used for withdrawing vapor from the lower end of thepressure vessel, and wherein the system includes additional outletpiping means used for withdrawing liquid from the lower end of thepressure vessel.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

[0051]FIG. 1 is a schematic drawing of a heat exchanger assemblyaccording to the present invention.

[0052]FIG. 2 is a schematic drawing of an alternative embodiment of theheat exchanger assembly according to the present invention.

[0053]FIG. 3 is a schematic drawing of another alternative embodiment ofthe heat exchanger assembly according to the present invention.

[0054]FIG. 4 is a schematic drawing of an embodiment of the presentinvention which utilizes two heat exchanger assemblies in series.

DETAILED DESCRIPTION OF THE INVENTION

[0055] The invention as described herein eliminates selected distributorfins, collector fins, headers, nozzles, and manifolds from plate-and-fincore-type heat exchangers typically used for low temperature gasprocessing. In the various embodiments of the invention, thesedistributor fins, collector fins, headers, nozzles, and manifolds areeliminated at the feed stream inlet, the processed stream outlet, orboth the feed stream inlet and the processed stream outlet of the heatexchanger. The invention can be utilized for cooling a fluid stream(i.e., a gas or a liquid stream) without phase change, or alternativelyfor partially or totally condensing a gas stream.

[0056] A first embodiment of the invention is illustrated in FIG. 1.Heat exchanger 1 is a typical plate-and-fin core-type heat exchanger asearlier described, and usually is installed in a generally verticalorientation inside pressure vessel 3. A portion of the flow passagewaysin the heat exchanger can be utilized for condensing service, and thesepassageways form a feed circuit through which the uncondensed feed gasand condensate flow cocurrently. The flow passageways are oriented suchthat the uncondensed feed gas and condensate flow cocurrently in agenerally downward direction, i.e., in a vertical downward direction orin a downward direction which deviates from vertical wherein the flowpassageways operate such that the condensate flows downward by the forceof gravity. The generally downward direction is preferably vertical butcan deviate from the vertical as long as the deviation does notadversely affect the downward cocurrent flow of uncondensed feed gas andcondensate through the exchanger and the transfer of heat from theuncondensed feed gas and condensate.

[0057] The bulk flow of vapor and liquid is generally parallel to theaxes of the flow passageways. The feed circuit heat transfer fin sectionextends to bottom 5 of heat exchanger 1, and the feed circuit is open atbottom 5 and is in full flow communication with the interior of pressurevessel 3. The term “open” means that the end of the exchanger has nocollector fins or headers associated with it, and therefore fluid canflow unimpeded without restriction from the end of each flow channel.Thus in FIG. 1 both vapor 7 and condensed liquid 9 flow unimpeded fromthe exchanger core without restriction, and the full fluid-handlingcapacity of the core therefore can be utilized.

[0058] A stream of mixed feed gas 11 enters inlet 13 of pressure vessel3, flows through manifolds 17 and 19, and flows through header 21through distributor fins (not shown) into the feed circuit of heatexchanger 1. The distributor fins are located at the entrance to thecore and function to direct fluid from the header into the main flowpassageways in the body of the core. The distributor fins can beconsidered as part of the plate-and-fin heat exchanger core. Manifold17, manifold 19, and header 21 are generically described as fluidtransfer means to transfer fluid from inlet 13 to the end of heatexchanger 1.

[0059] The feed gas flows downward in this embodiment and is partiallycondensed therein by refrigeration provided in adjacent flow channels asdescribed below. Condensate 9 drains freely from the feed circuit at thebottom of the core and collects in the bottom of vessel 3, from whichliquid product stream 23 is withdrawn through vessel outlet 25.Uncondensed vapor 7 exits exchanger 1 via vessel outlet 27 to providevapor product stream 29. This arrangement eliminates the need for aseparator drum to separate the condensed liquid from the uncondensedvapor portion of the cooled feed.

[0060] Vapor product stream 29 is enriched in the lower boiling, morevolatile components in the feed gas mixture and liquid product 23 isenriched in the higher boiling, less volatile components in the feed gasmixture. The feed gas mixture contains more volatile components and lessvolatile components, and the mixture typically contains two or morecomponents selected from the group consisting of hydrogen, helium,carbon monoxide, carbon dioxide, nitrogen, argon, oxygen, and C, to C₆hydrocarbons. Feed gas mixtures can include cracked gas, refinery andpetrochemical plant offgases, synthesis gas, natural gas, and air.

[0061] Typical refrigerant stream 31 is introduced via vessel inlet 33,manifolds 35 and 37, header 39, and distributor fins (not shown) into arefrigerant circuit which comprises a group of flow channels in the coreof heat exchanger 1. Refrigerant flows upward through the refrigerantcircuit in heat exchanger 1 while warming and/or vaporizing to provideindirect cooling to the condensing vapor in the feed circuit describedearlier. Warmed refrigerant is withdrawn from the heat exchanger throughcollector fins (not shown), header 41, manifolds 43 and 45, and outlet47 to provide warmed refrigerant stream 49.

[0062] Refrigerant 31 can be a cold process fluid which is warmed toprovide sensible and/or latent heat for cooling and condensing the feedgas. Alternatively, a liquid refrigerant can be used which vaporizeswhile flowing through the refrigerant circuit. The liquid refrigerantcan flow downward if desired. Typical refrigerants can be selected fromC₁ to C₃ hydrocarbons, ammonia, fluorocarbons, chlorofluorocarbons, andmixed refrigerants which are recirculated through a closed-looprefrigeration circuit. More than one refrigerant circuit can be used ifdesired, which would require additional header and distributor/collectorsystems at the top and bottom of heat exchanger 1.

[0063] Additional heat exchangers can be installed in parallel with heatexchanger 1 in pressure vessel 3 if desired. An additional heatexchanger 51, for example, is shown in FIG. 1 and operates in parallelwith heat exchanger 1. Feed gas 11 is introduced into the feed circuitof heat exchanger 51 via inlet 13, manifold 17, manifold 53, distributorheader 55, and distributor fins (not shown). Uncondensed vapor 59 andcondensate 61 flow from the bottom of exchanger 51 in a similar mannerto the flows from heat exchanger 1. Refrigerant 31 for heat exchanger 51enters via inlet 33, manifolds 35 and 55, and distributor header 57 andfins. Warmed refrigerant is withdrawn from heat exchanger 51 viacollector fins and header 63, manifolds 65 and 45, and outlet 47.

[0064] Typical operating temperatures and pressures range from +100° F.to 400° F. for feed and refrigerants, 100 to 1500 psia for the feed, and2 to 1500 psia for refrigerants.

[0065] When parallel heat exchanger cores are used, inlet and outletlines can be manifolded inside pressure vessel 3 as shown to reduce thenumber of pipes passing through the vessel shell, although this is notnecessary. Refrigerant drums, which may be used for ethylene, propylene,or similar thermosiphon-type refrigerant circuits, or for distributingtwo-phase refrigerant streams into the heat exchanger cores, can belocated inside or outside the pressure vessel as desired. The pressurevessel can be externally insulated, similar to a distillation column, sothat no cold box is required, particularly where operating temperaturesare above about −250° F.

[0066] Alternatively, it may be desirable to have the feed gas 11 enterand/or leave the sides, rather than the ends, of heat exchangers 1 and51 (not shown). In this case, distributor and/or collector fins would berequired at one or both ends of the core to distribute flow into and/orcollect flow from the cores. The corresponding distributors orcollectors would be open to the interior of pressure vessel 3 on theside of the core to permit feed gas to enter and/or leave the core.Headers, nozzles and manifolds would not be required for the open sidesof the cores.

[0067] While the heat exchanger as described above is utilized forcondensing flow, the heat exchanger alternatively can be utilized tocool a fluid (either gas or liquid) without phase change. For example, asuperheated gas stream can be cooled to a temperature above its dewpoint, while a liquid at or below its bubble point can be subcooled to atemperature further below its bubble point. In this alternative, theaxis of the heat exchanger and the flow direction of the fluid beingcooled (which is generally parallel to the axis of the exchanger) can bevertical, horizontal, or between vertical and horizontal. Thus the fluidbeing cooled can flow in any desired direction.

[0068] An alternative embodiment is shown in FIG. 2 which can be usedwhen the feed gas is to be cooled or partially condensed in an upwardflow direction, or when it is desirable to remove the vapor and liquidportions of the cooled and partially condensed gas as a mixed streamrather than as separate vapor and liquid streams. In this arrangement,feed gas 11 is introduced via inlet 201 of pressure vessel 203, and feedgas 205 flows into the open ends of heat exchangers 207 and 209. The gascondenses as it flows upward with the resulting condensate, and thetwo-phase vapor/liquid stream is withdrawn via collector fins andheaders 211 and 213, manifolds 215, 217, and 219, and outlet 221 toprovide final vapor/liquid product 223. Headers 211 and 213 andmanifolds 215, 217, and 219 are generically described as fluid transfermeans to transfer fluid from the ends of heat exchangers 207 and 209 tooutlet 221. The refrigerant in this alternative embodiment can beprovided as described earlier for the embodiment of FIG. 1.

[0069] The flow passageways are oriented such that the cocurrent flow ofuncondensed feed gas and condensate is in a generally upward direction,i.e., in a vertical upward direction or in an upward direction which isbetween vertical and horizontal. The flow passageways deviatesufficiently from the horizontal such that the condensate flows upwardby entrainment in the upward-flowing gas. Preferably, the flow is in agenerally upward direction, which means that the flow is preferablyvertically upward but can deviate from the vertical as long as thedeviation does not adversely affect the upward cocurrent flow ofuncondensed feed gas and entrained condensate through the exchangerand/or the transfer of heat from the uncondensed feed gas and condensateto the refrigerant. The refrigerant can flow upward as shown using avaporizing fluid, or downward using a gaseous refrigerant, to maintainan adequate temperature difference between the feed and the refrigerant.

[0070] In the embodiments of FIGS. 1 and 2, heat exchangers 1 and 209are open at the bottom and have a header and manifolds at the top of theexchanger. In an alternative embodiment (not shown), the heat exchangeris open at the top and has a header and manifolds at the bottom. Fluidflow in this alternative embodiment can be either upward or downward,and can be either single-phase or condensing flow as described above.

[0071] Another alternative embodiment of the invention is shown in FIG.3 which illustrates the use of two heat exchangers in parallel, althoughsingle or more than two heat exchangers can be used if desired. In thisembodiment, heat exchangers 301 and 303 are installed in pressure vessel305, and seal means 307 (shown schematically) is installed between theheat exchanger and pressure vessel walls to segregate the vesselinterior into upper section 309 and lower section 311 which are not inflow communication. Seal means 307 can be installed at any appropriateaxial location between the upper and lower ends of heat exchangers 301and 303. Seal means 307 can be any type of seal known in the art forsegregating the upper and lower sections of the vessel against a low gaspressure differential, for example, 1 to 10 psi. Seal means 307 could beintegrated with a core or piping support member.

[0072] The use of seal means 307 eliminates the need for feeddistributor fins, headers, and manifolds at the top of the heatexchangers and processed gas collector fins, headers, and manifolds atthe bottom of the heat exchangers. Thus the flow passageways or channelsare open at both ends. The term “open” means that the end of theexchanger has no distributor fins, collector fins, or headers associatedwith it, and therefore fluid can flow unimpeded without restriction intoand out of the ends of the flow channels. The heat transfer fins in theflow passageways can be continuous from the top to the bottom of thecore, with no distributor or collector fins at either end. The bottomend of each feed channel is in flow communication with lower section 311of pressure vessel 305, and the upper end of each feed channel is inflow communication with upper section 309 of the pressure vessel. Therefrigerant circuits can be similar to those described in FIG. 1.

[0073] A portion of the flow passageways in the heat exchanger can beutilized for condensing service, and these passageways form a feedcircuit through which the uncondensed feed gas and condensate flowcocurrently. The flow passageways are oriented such that the uncondensedfeed gas and condensate flow cocurrently in a generally downwarddirection, i.e., in a vertical downward direction or in a downwarddirection which deviates from vertical wherein the flow passagewaysoperate such that the condensate flows downward by the force of gravity.The generally downward direction is preferably vertical but can deviatefrom the vertical as long as the deviation does not adversely affect thedownward cocurrent flow of uncondensed feed gas and condensate throughthe exchanger and/or the transfer of heat from the uncondensed feed gasand condensate to the refrigerant.

[0074] In this embodiment, feed gas stream 313 flows through vesselinlet 315, and interior feed gas 317 flows into upper section 309 ofvessel 305 and then downward through the feed channels of heatexchangers 301 and 303. Condensation occurs as the gas and condensateflow downward through the feed channels, liquid 319 flows from the openends of heat exchangers 301 and 303, and liquid 321 collects in thebottom of the vessel. Liquid product 323 is withdrawn via outlet 325 anduncondensed vapor 327 flows directly from the open feed channels at thelower ends of the heat exchangers and is withdrawn via vessel outlet 329to provide vapor product 331.

[0075] While the heat exchanger of FIG. 3 as described above is utilizedfor condensing flow, the heat exchanger alternatively can be utilized tocool a fluid (either gas or liquid) without phase change. For example, asuperheated gas stream can be cooled to a temperature above its dewpoint, while a liquid at or below its bubble point can be subcooled to atemperature further below its bubble point. In this alternative, theaxis of the heat exchanger and the flow direction of the fluid beingcooled (which is generally parallel to the axis of the exchanger) can bevertical, horizontal, or between vertical and horizontal. Thus the fluidbeing cooled can flow in any desired direction.

[0076] The advantage of the embodiment of FIG. 3 is that no manifolds,headers, distributor fins, or collector fins are needed at either end ofheat exchangers 301 and 303 for feed introduction and productwithdrawal. This greatly simplifies the entire heat exchanger assemblyand results in reduced capital cost.

[0077] Two or more heat exchanger cores operating in differenttemperature or pressure ranges can be utilized in series or in parallelby stacking the pressure vessels in a vertical arrangement or bylocating the vessels side-by-side. When used in series, the exit gasfrom a first heat exchanger is fed to a second heat exchanger forfurther cooling as described below. An internal head can be used insidea single pressure vessel to separate the warmer and colder heatexchangers as shown in the alternative embodiment of FIG. 4. In thisembodiment, lower pressure vessel section 401 and upper pressure vesselsection 403 are formed by head 405 installed in overall pressure vessel407. Lower pressure vessel 401 and heat exchangers 409 and 411 installedtherein are similar to the system described above for FIG. 3. Upperpressure vessel 403 and heat exchangers 413 and 415 are similar to thesystem described earlier for FIG. 1.

[0078] Feed gas 417 is processed in heat exchangers 413 and 415 in thesame manner as that described earlier for exchangers 1 and 51 for theembodiment of FIG. 1. Intermediate vapor product 419 flows throughvessel inlet 421 into upper portion 423 of pressure vessel 401, and isprocessed in the same manner as that described earlier for theembodiment of FIG. 3. First liquid product 425 is withdrawn via outlet427. Vapor 429 condenses further in exchangers 409 and 411, whichoperate with a colder refrigerant than exchangers 413 and 415.

[0079] Additional liquid is condensed and condensate 431 flows out ofthe bottoms of heat exchangers 409 and 411, and collects in the bottomof vessel 401 as liquid 433. This liquid is withdrawn via outlet 435 toprovide second liquid product stream 437, which contains additionalhigher boiling components. Vapor 439 flows from the bottoms of heatexchangers 409 and 411, and vapor product 441 is withdrawn via outlet443. This vapor product is enriched in the more volatile components infeed gas 417.

[0080] Refrigerant 445 provides refrigeration to heat exchangers 413 and415 as described earlier for the operation of heat exchangers 1 and 51of FIG. 1. Refrigerant 449, which is at a lower temperature thanrefrigerant 445, provides refrigeration to heat exchangers 409 and 411as described earlier for the operation of heat exchangers 301 and 303 ofFIG. 3. The two sections of vessel 407 can utilize different numbers orsizes of heat exchangers, and the sections may be of differentdiameters.

[0081] The two vessel sections of FIG. 4 can be operated at differentpressures if desired. In this mode of operation, vessel section 403 isoperated at a higher pressure than vessel section 401, and uncondensedgas stream 419 is reduced in pressure before being introduced into inlet421.

[0082] Several alternatives to the embodiment of FIG. 4 are possible. Inone alternative, upper section 403 can be similar to bottom section 401,wherein both sections utilize heat exchangers open on both ends withseals to segregate the upper and lower portions of the exchangers. Inanother alternative, the bottom section 401 would contain heatexchangers identical to those in upper section 403 of FIG. 4. In yetanother alternative, heat exchangers 409 and 411, with seal 447, can belocated in upper section 403 while heat exchangers 413 and 415, with gasinlet headers and distributor fins, can be located in lower section 401.

[0083] In another alternative, an internal head or other arrangement,such as a chimney tray (not shown), can be used inside a single pressurevessel to separate the heat exchangers in sections 401 and 403. In thisalternative, the vapor from the upper section can flow by means of thechimney tray directly into the lower section without flowing throughexternal piping required for stream 419 of FIG. 4. The two sections ofthe pressure vessel can contain the same size or different sizes of heatexchangers, can contain the same or different numbers of heatexchangers, and can be of different diameters if necessary. The feed gascan flow either upward or downward in each of the heat exchangers asdescribed earlier. The feed inlet, the processed gas/liquid outlet, orboth the feed inlet and processed gas/liquid outlet of each of the heatexchangers can be open to the interior of the pressure vessel.

[0084] A common feature of all embodiments of the invention describedabove operating in condensing flow is that condensed liquid anduncondensed vapor flow through the channels of the core-type heatexchangers cocurrently, i.e., in the same direction. Preferably, flow isin a generally downward direction, but upward flow is used in at leastone alternative embodiment as described above. When upward flow is used,the heat exchangers must be designed so that the upward gas flowvelocity is sufficient to entrain the condensate such that essentiallynone of the condensate flows in a downward direction.

[0085] As discussed earlier, conventional full dome header distributorand collector devices typically cannot be used on cores larger thanabout 3 feet by 4 feet in cross section at pressures above about 150psig. The pressure vessel for the present invention, however, can bedesigned to operate at any pressure level, preferably in the range of100 to 1500 psia. The heat exchanger cores can be any size, both incross-section and in length. Welded-blocks, i.e. two or more coreswelded together side-by-side, can be utilized to increase the availablecross-section of the heat exchanger cores to a very large size, such as4 feet by 8 feet or more. Any length of core can be used, and istypically in the range of 5 to 20 feet.

[0086] The pressure vessel can be externally insulated, similar to adistillation column, so that no cold box is required for the heatexchangers. When parallel heat exchanger cores are used, the number ofpipes which must pass through the pressure vessel shell can be minimizedby manifolding refrigerant stream nozzles inside the pressure vessel.Refrigerant drums can also be located either inside or outside thepressure vessel, as desired.

[0087] In other alternative embodiments, three or more heat exchangers,each operating at progressively colder temperatures, can be installed inseries within a single pressure vessel, or in separate vessels, or acombination of stacked and separate pressure vessels. Any combination offeed flow direction and open core ends/sides can be used in each of theheat exchangers. All refrigerant streams entering or leaving the heatexchangers typically would utilize conventional distributors,collectors, headers, and nozzles, which are piped through the vesselshell.

[0088] When two or more heat exchangers are utilized in series in eitherstacked or separate pressure vessels, one or more of the heat exchangerscan be replaced by a dephlegmator. In the dephlegmator, feed gas entersthe pressure vessel, flows into the open bottom end of the core andupward through the core. Condensed liquid drains downward, andrectification occurs as the liquid and vapor flow countercurrently inthe core. Condensate exits freely from the bottom of the core into thebottom of the vessel for removal. The feed vapor outlet at the top endof the dephlegmator may be either open or closed. All refrigerantstreams entering or leaving the dephlegmator typically would utilizeconventional distributors, collectors, headers, and nozzles.

[0089] Thus the present invention simplifies the design of plate-and-finheat exchanger cores which operate in the condensing mode and allowsefficient use of the core cross section because no manifolds,distributor fins, and headers are required at the inlet of each feedcircuit. In an optional embodiment, vapor collector fins, manifolds, andheaders are not required at the outlet of each feed circuit, furthersimplifying heat exchanger design and operation. The present inventionallows operation of plate-and-fin core-type heat exchangers at higherpressures than many prior art systems which require dome headers orsimilar integrated vessels attached to the heat exchanger feed circuits.In addition, higher throughput is possible because the available fluidhandling capacity of each heat exchanger is not reduced by distributors,collectors, headers, nozzles, or manifolds.

[0090] The essential characteristics of the present invention aredescribed completely in the foregoing disclosure. One skilled in the artcan understand the invention and make various modifications withoutdeparting from the basic spirit of the invention, and without deviatingfrom the scope and equivalents of the claims which follow.

1. A system for cooling a fluid feed stream which comprises: (a) apressure vessel having an interior and an exterior; (b) a heat exchangerinstalled in the interior of the pressure vessel, wherein the heatexchanger comprises a group of flow passageways which has a first endand a second end, wherein at least one of the first end and the secondend is open and in flow communication with the interior of the pressurevessel; (c) inlet piping means for introducing the fluid feed streaminto the interior of the pressure vessel; (d) outlet piping means forwithdrawing from the interior of the pressure vessel at least a portionof the cooled fluid stream; (e) cooling means for indirectly cooling thegroup of flow passageways to cool the fluid feed stream therein to forma cooled fluid stream; and (f) fluid transfer means for transferring thefluid feed stream from the inlet piping means into the group of flowpassageways at one end thereof or for transferring a cooled fluid streamfrom one end of the group of flow passageways to the outlet pipingmeans.
 2. The system of claim 1 wherein the heat exchanger isconstructed in a plate-and-fin configuration.
 3. The system of claim 1wherein the cooling means of (e) comprises (1) one or more additionalgroups of flow passageways in the heat exchanger wherein each additionalgroup of flow passageways has a first end and a second end, and whereineach additional group of flow passageways is in indirect heat transfercommunication with the group of flow passageways of (b); (2) inletpiping means for introducing refrigerant into the interior of thepressure vessel; (3) outlet piping means for withdrawing warmedrefrigerant from the interior of the pressure vessel; (4) inletdistributor means for distributing the refrigerant from the inlet pipinginto the first end of the additional group of flow passageways; and (5)outlet collector means for collecting the warmed refrigerant from thesecond end of the additional group of flow passageways and directingwarmed refrigerant into the outlet piping means.
 4. The system of claim1 which further comprises (g) an additional pressure vessel having aninterior and an exterior; (h) a heat exchanger installed in the interiorof the additional pressure vessel, wherein the heat exchanger comprisesa group of flow passageways which has a first end and a second end,wherein at least one of the first end and the second end is open and inflow communication with the interior of the additional pressure vessel;(i) inlet piping means for introducing an intermediate fluid stream intothe interior of the additional pressure vessel; (j) cooling means forindirectly cooling the group of flow passageways to cool theintermediate fluid stream therein to form an additional cooled fluidstream; (k) outlet piping means for withdrawing from the interior of theadditional pressure vessel at least a portion of the additional cooledfluid stream; and (l) fluid transfer means for transferring the fluidfeed stream from the inlet piping means into the group of flowpassageways at one end thereof or for transferring a cooled fluid streamfrom one end of the group of flow passageways to the outlet pipingmeans.
 5. The system of claim 4 which further comprises piping meansconnecting the outlet piping means of (d) with the inlet piping means of(i) such that at least a portion of the cooled fluid stream withdrawnfrom the pressure vessel can provide the intermediate fluid stream tothe additional pressure vessel.
 6. The system of claim 1 wherein thefirst end of the flow passageways is an upper end and the second end ofthe flow passageways is a lower end, and wherein the lower end is openand in flow communication with a lower region in the interior of thepressure vessel.
 7. The system of claim 6 wherein the heat exchanger isconstructed in a plate-and-fin configuration.
 8. The system of claim 6wherein the fluid transfer means comprises outlet manifold means andoutlet header means for transferring a cooled fluid stream from theupper end of the group of flow passageways to the outlet piping.
 9. Thesystem of claim 8 wherein the inlet piping means is connected to a lowerend of the pressure vessel and the outlet piping means is connected toan upper end of the pressure vessel such that fluid can flow through thegroup of flow passageways in a generally upward direction.
 10. Thesystem of claim 6 wherein the fluid transfer means comprises inletmanifold means and inlet header means for transferring the fluid feedstream from the inlet piping into the upper end of the group of flowpassageways.
 11. The system of claim 10 wherein the inlet piping meansis connected to an upper end of the pressure vessel and the outletpiping means is connected to a lower end of the pressure vessel suchthat fluid can flow through the group of flow passageways in a generallydownward direction.
 12. The system of claim 11 wherein the fluid flowinggenerally downward through the group of flow passageways is a gas whichcan condense therein to form a vapor and a liquid which flow into thelower end of the pressure vessel, wherein the outlet piping means of (d)is used for withdrawing vapor from the lower end of the pressure vessel,and wherein the system includes additional outlet piping means used forwithdrawing liquid from the lower end of the pressure vessel.
 13. Thesystem of claim 6 which further comprises (g) an additional pressurevessel having an interior and an exterior; (h) a heat exchangerinstalled in the interior of the additional pressure vessel, wherein theheat exchanger comprises a group of flow passageways which has a firstend and a second end, wherein at least one of the first end and thesecond end is open and in flow communication with the interior of theadditional pressure vessel; (i) inlet piping means for introducing anintermediate fluid stream into the interior of the additional pressurevessel; (j) inlet fluid transfer means for transferring the intermediatefluid stream from the inlet piping means into the group of flowpassageways at one end thereof; (k) cooling means for indirectly coolingthe group of flow passageways to cool the intermediate fluid streamtherein to form an additional cooled fluid stream; and (l) outlet pipingmeans for withdrawing from the interior of the pressure vessel at leasta portion of the additional cooled fluid stream.
 14. The system of claim13 which further comprises piping means connecting the outlet pipingmeans of (d) with the inlet piping means of (i) such that at least aportion of the vapor withdrawn from the pressure vessel can provide theintermediate fluid stream to the additional pressure vessel.
 15. Thesystem of claim 14 wherein the heat exchanger in the additional pressurevessel is constructed in a plate-and-fin configuration.
 16. The systemof claim 14 wherein the inlet piping means is connected to an upper endof the additional pressure vessel and the outlet piping means isconnected to a lower end of the additional pressure vessel such thatvapor can flow through the group of flow passageways in a generallydownward direction.
 17. The system of claim 16 wherein the vapor flowinggenerally downward through the group of flow passageways can condensetherein to form an uncondensed vapor and a liquid which flow into thelower end of the additional pressure vessel, wherein the outlet pipingmeans of (I) is used for withdrawing the uncondensed vapor from thelower end of the additional pressure vessel, and wherein the systemincludes additional outlet piping means used for withdrawing liquid fromthe lower end of the additional pressure vessel.
 18. The system of claim1 wherein the first end of the flow passageways is an upper end and thesecond end of the flow passageways is a lower end, and wherein the upperend is open and in flow communication with an upper region in theinterior of the pressure vessel.
 19. The system of claim 18 wherein theheat exchanger is constructed in a plate-and-fin configuration.
 20. Thesystem of claim 18 wherein the fluid transfer means comprises inletmanifold means and inlet header means for transferring the fluid feedstream from the inlet piping into the lower end of the group of flowpassageways.
 21. The system of claim 20 wherein the inlet piping meansis connected to a lower end of the pressure vessel and the outlet pipingmeans is connected to an upper end of the pressure vessel such thatfluid can flow through the group of flow passageways in a generallyupward direction.
 22. The system of claim 18 wherein the fluid transfermeans comprises outlet manifold means and outlet header means fortransferring the cooled fluid stream from the lower end of the group offlow passageways to the outlet piping means.
 23. The system of claim 21wherein the inlet piping means is connected to an upper end of thepressure vessel and the outlet piping means is connected to a lower endof the pressure vessel such that fluid can flow through the group offlow passageways in a generally downward direction.
 24. A system forcooling a fluid feed stream which comprises: (a) a pressure vesselhaving an interior and an exterior; (b) a heat exchanger installed inthe interior of the pressure vessel, wherein the heat exchangercomprises a group of flow passageways having a first end and a secondend, wherein the first end is open and in flow communication with afirst end of the interior of the pressure vessel and the second end isopen and in flow communication with a second end of the interior of thepressure vessel; (c) cooling means for indirectly cooling the group offlow passageways to cool the fluid feed stream therein to form a cooledfluid stream; (d) inlet piping means for introducing the fluid feedstream into the first end of the interior of the pressure vessel; (e)outlet piping means for withdrawing at least a portion of the cooledfluid stream from the second end of the interior of the pressure vessel;and (f) seal means disposed in the pressure vessel at an axial locationbetween the first and second ends of the group of flow passageways,which seal means isolates the first end of the interior of the pressurevessel from the second end of the interior of the pressure vessel suchthat the first and second ends of the interior of the pressure vesselare not in flow communication.
 25. The system of claim 24 wherein theheat exchanger is constructed in a plate-and-fin configuration.
 26. Thesystem of claim 24 wherein the inlet piping means is connected to alower end of the pressure vessel and the outlet piping means isconnected to an upper end of the pressure vessel such that fluid canflow through the group of flow passageways in a generally upwarddirection.
 27. The system of claim 24 wherein the inlet piping means isconnected to an upper end of the pressure vessel and the outlet pipingmeans is connected to a lower end of the pressure vessel such that fluidcan flow through the group of flow passageways in a generally downwarddirection.
 28. The system of claim 27 wherein the fluid flowinggenerally downward through the group of flow passageways is a gas whichcan condense therein to form a vapor and a liquid which flow into thelower end of the pressure vessel, wherein the outlet piping means of (e)is used for withdrawing vapor from the lower end of the pressure vessel,and wherein the system includes additional outlet piping means used forwithdrawing liquid from the lower end of the pressure vessel.